Nonblurrable mirror



Aug. 21, 1951 c. w. ELSENHEIMER N ONBLURRABLE MIRROR Filed Feb. 2, 1949CHARLES w. ELSENHElMER PATENT AGENT FIG.4.

Patented Aug. 21, 1951 N ONBLURRABLE MIRROR Charles W. Elsenheimer,Meriden, Conn., assignor to- The Charles Parker Company, Meriden,

Conn.

Application February 2, 1949, Serial No. 74,101

2 Claims.

. The present invention relates to a so-called non-blurrable mirror, i.e. a mirror having a mirror plate, on the front face of whichcondensation of water vapor is prevented, such condensation tending tofog or mist the front face of the mirror plate. These non-blurrablemirrors are primarily useful in bath and shower rooms in which usuallythe condensation of water vapor is so great that the faces of normalmirror plates have to be frequently wiped or dried to obtain a clear andtrue reflection.

The primary object of the present invention is the provision of anelectric heating element or resistance unit of simple, inexpensive anddurable construction in intimate contact with the back of the mirrorplate, said heating element or unit being adapted to heat said mirrorplate to such temperature that condensation of water vapor or moisturecannot occur upon the face of the mirror plate.

Another object of this invention is to provide a mirror plate, to therear of which a flexible heating unit is applied in such a manner thatit snugly contacts said rear substantially over the whole area.

A further object of the invention is a mirror plate in intimate contactwith a substantially flat heating element or resistance unit comprisinga flexible sheet of a composition, such as a rubber composition,rendered electrically conducting by incorporation of finely dividedelectrically conducting particles, such as carbon black, opposite edgesof said sheet being con' nected to a source of electric current in sucha manner that said sheet is uniformly heated and conveys its heat to themirror plate thereby preventing condensation of water vapor on themirror face.

Other and further objects and advantages of the present invention willbe apparent from the following description and claims and areillustrated in the accompanying drawings showing, by way of example,preferred embodiments and the principle thereof and what the inventorconsiders now to be the best mode of applying said principle. Otherembodiments of the invention embodying the same or equivalent principlesmay be used and structural changes may be made as desired by thoseskilled in the art without departing from the present invention and thepurview of the appended claims.

In the drawings,

Fig. 1 is a front view of the mirror embodying this invention, partlybroken away to show the underlying construction.

Fig. 2 is a cross section through the mirror of Figure 1, taken alongthe line 2--2, showing the heating unit.

Fig. 3 is a cross section illustrating a modified embodiment of theheating unit, taken along the line 2-2 of Fig. l.

Fig. 4 is a cross section showing a further modification of the heatingunit, taken likewise along the line 22 of Fig. 1.

With reference to Figures 1 and 2 of the drawing, I0 indicates a casingmade of any suitable material, such as metal, plastic, or wood,comprising a front frame ll, open at l2, of preferably rectangular shapewith bent edges or flanges l3 defining the depth of the casing. A rearor lid member I 4 of similar dimensions, shape and material as saidframe H is likewise provided with bent edges or flanges l5 adapted toengage intimately the edges or flanges iii of said frame I I at theirinner sides in such a manner that a box-like casing of relatively smalldepth is obtained. The engaging flanges l3 and It may be firmly joinedin a suitable manner, for example, by bolts, soldering, welding, etc.

S-shaped clamps or holding means It for a mirror plate I? are mounted onthe inside of the front frame H at proper locations, so that said mirrorplate H which is slightly larger than the front opening [2 of said framell covers the opening l2, while the edges of said mirror plate ll extendslightly beyond the rim of said opening. These S-shaped clamps orholding means l6 made of metal or plastic material are secured to saidframe H, for example by means of rivets, screws, or by spot-welding. Themirror plate I? in the present embodiment is made of plate glass treatedor coated on the rear side in the usual manner to provide a reflectingrear surface l8, while the opposite side or front face It of the mirrorplate is uncoated and trans parent. In place of such plate glass mirrorof normal construction, other types of mirror plates, including mirrorplates of metal may be used.

A fl'at heating unit 29 of substantially the same area as the mirrorplate I1 is inserted between the rear [8 of said plate I! and the free,bent portions i511, of the S-shaped clamps or holding means N5 of saidplate l1, said clamps or holding means I 6 supporting the heating unit25 and holding it resiliently under slight pressure against the rear [8of the mirror plate H. This heating unit may be cemented to said rear 8The empty space within the box-like cas-= ing, behind the heating unit20, may be filled with a suitable inexpensive filler 2| having re 3,fractory or heat-insulating properties, for example with rockwool,cardboard, etc. to prevent heat losses and separation of the heatingunit 20 from the rear of the mirror plate H at the places, where noclamps H are applied, and to assure an intimate contact between the rearl8 of the mirror plate l1 and the heating unit 20 throughout the wholesurface area.

The heating unit 20 has three layers, the two outer ones 22 and 23 beingmade of sheets of equal area of ordinary, soft, flexible, electricallyinsulating rubber, while the intermediate or center layer '24 formingthe resistance member proper is a sheet of an electrically conductingrubber composition, which may be prepared as described in U. S. PatentNo. 2,255,376 by incorporating or dispersing uniformly conductingparticles, such as carbon black, into the rubber mixture during itsprocess of manufacture. In place of this rubber composition sheet, anyother flexible composition sheet rendered conducting by anyprocess otherthan described in the aforementioned United States patent may be used.These two insulating layers 22 and 23 and the intermediate conductingsheet '24 are joined by vulcanizing, resulting in an integral structureforming the heating unit 20. Conductors or wires 25 and 26 are attachedto and along two opposite marginal portions of said conducting sheet 24,said two conductors or wires running across substantially the entirewidth of said sheet 24. Preferably these conductors or wires 25 and 26are tinned at their places of contact with said sheet 24, i. e. they aretinned along the whole length of the edges of said conducting sheet 24.To assure a firm contact with the sheet 24, said conductors or wires 25and 26 are solidly secured to the heating unit 23 during thevulcanization of the three sheets constituting said unit. The mechanicalconnection between said conductors or wires 25 and 23 and the edges ofsaid sheet 24 may be further improved by folding the marginal portionsof said edges of the conducting sheet 24 around the conductors or wires25 and 26, as is described in the aforementioned U. S. Patent No.2,255,376. The bent portions |6a of said clamps |6 at the top and thebottom of said heating unit 26 exert pressure primarily at thelocations, where the conductors or wires 25 and 26 are secured to saidmarginal portions across said conducting sheet 24, thus assuring a firmcontact along said portions which will not be impaired by or during theheating of said unit 20.

A thermostatic switch 21 of suitable construction and characteristic maybe mounted in the casing ID at a suitable place and may be electricallyconnected or inserted in the electric heating circuit of the unit. Inthe present embodiment shown in Fig. 2, said thermostat 21 is mounted inthe upper part of the casing Ill, and the wire 26 is leading to saidthermostat. A wire 38 connects the thermostat 21 with a manual switch 28to be operated by the user of the mirror. An outgoing wire 29 connectedto said manual switch 28 and the wire 25 directly attached to saidconductive sheet 24 can be connected to any electric network in theusual manner.

When the manual switch 28 is closed, the circuit through said conductingsheet 24 is completed. Said sheet is traversed substantially uniformlyby the energizing current, because the wires 25 and 26 are connected orattached to said sheet 24 along the entire length of its edges. As aresult of this, a uniform current density throughout the whole sheet 24and consequently 4 a uniform heat distribution over the whole sheetsurface is obtained. The heat produced in the sheet 24 is readilyconveyed to the rear |8 of said mirror plate due to the intimate contactwith the heating unit 20 and to the front face I9 of said mirror plate,on which vapor condensation or moisture is prevented or rapidly removed.The thermostat 21 controls the temperature of the heating unit 20 in aconventional manner. The

primary advantage of the provision of this thermostat in the presentdevice is that the heating unit 20 can be dimensioned for a highercurrent density resutling in a quicker heating action and prevention ofany condensation on the mirror face, whereby overheating is safelyprevented by the intermittent operation of the heating unit 20 undercontrol of said thermostatic switch 21.

The modified heating unit 3|], shown in Fig. 3, comprises only tworubber layers, 1. e. an electrically conducting rubber sheet 3| of thesame properties as the intermediate sheet 24 in Fig. 2 and anelectrically insulating rubber layer 32 similar to layer 23 in Fig. 2.These two sheets or layers 3| and 32 may be joined to form the integralheating unit 33 by the same vulcanization step indicated in theforegoing with respect to the manufacture of the heating unit 26, shownin Fig. 2, whereby likewise the wires 25 and 26 will be secured to theconducting sheet 3| by vulcanization. According to Fig. 3, theelectrically conducting rubber sheet 3| is directly pressed against therear 18 of the mirror plate glass while the electrically insulatinglayer 32 is facing the bent portions |6a and the filler material 2| inthe rear of the casing H). The heating unit 30 may be cemented to therear l8 of the mirror plate If the mirror plate is of metal, aninsulating coating may be provided on the rear I8 and/or on that side ofthe electrically conducting sheet 3| which contacts said rear I3.

In a further modification of the heating unit, shown in Fig. 4, one sideof flexible pane] or sheet 33 of any kind of electrically insulating andheat resistant material, such as fiber, asbestos, woven glass, orplastic, is treated or provided with a coating 34 of an electricallyconducting material or cement, which may be made of the same rubbercomposition as the conducting sheets 24 and. 3| in Figs. 2 and 3,respectively. This conducting coating 34 may be applied to said panel orsheet 33 .by dipping, painting, or spraying. The wires 25 and 26 may beconnected to the conducting coating 34 in principally the same manner asin the embodiments of the heating units 20 and 3|], shown in Figs. 2 and3, respectively. The joint between the coating 34 and the'wires 25 and26 is improved and an integral heating unit 35 obtained by vulcanizationas in the previous embodiments. The heating unit 35, as shown in Fig. 4,is pressed against the rear l3 of the mirror glass plate H, with thecoated side 34 facing said rear, by means of the clamps H5 in the samemanner as inthe embodiments of Figs. 2 and 3. The heating unit 35 may becemented to said rear IS.

The new non-blurrable mirror construction may be combined or associatedwith any kind of fixture or furniture, in particular with the doors ofmedicine cabinets in bath and shower rooms. The heating unit can beapplied without difficulties to arched mirror plates, because it isflexible. As the heating unit is made of soft or resilient material,such as rubber compositions, it constitutes a good backing or cushionedsupport for the adjacent mirror glass plate. Consequently the latterwill not crack, when heated or otherwise subjected to mechanicalstresses. A further advantage of the inventive structure is that theheating unit can be easily installed in the present fixtures or piecesof furniture without necessitating major changes thereof. The heatingunit can be cut to any shape and size of mirror plate to which it is tobe applied. The new mirror may be applied to various instruments inwhich condensation on the reflectors is disturbing. For example, theinvention may be applied to dentists mirrors.

I claim:

1. A non-blurrable mirror comprising in combination, a mirror platehaving a front and a rear surface-and a mirror coating on said rearsurface, a flexible and compressible electrical heating unit coveringsaid rear surface and snugly applied thereto, said heating unitincluding an electrically conducting layer of a rubber-like comositionof substantially the same area as said heating unit, said compositioncontaining carbon black uniforml dispersed therein, electric conductorsadapted to be connected to a source of electric current, said conductorsbeing firmly attached to two opposite edges of said layer along theentire lengths of said edges, and means adapted to clamp said heatingunit to said mirror plate at the places of connection between saidconductors and said edges.

2. A non-blurrable mirror comprising in com- S-shaped clamping membersadapted to support 7 said mirror plate and said heating unit and holdingthem under slight pressure against each other and the mirror plateagainst the rim of the opening of said casing primarily at the places ofelectric contact between said electric connecting means and said heatingunit, said S-shaped clamping members being secured to the front wallinside said casing.

CHARLES W. ELSENHEIMER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,015,816 Pyzel Oct. 1, 19352,255,376 Bull et a1 Sept. 9, 1941 2,404,736 Marick July 23, 1946

